Telephone system



Dec. 20, 1938. E. P. G. WRIGHT ET A1. 2,140,931

TELEPHONE SYSTEM Filed Aug. 20, 1956 4 sheets-sneer 1 E. P. a. wR/GHr/NVEA/ToRs.- c. 2. HAR ner n Wmo/MM By @www TTORNE V Dec. 2o, 1938.

E. P, G, WRIGHT ET A1.

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E. P. G. WRIGHT ET AL TELEPHONE SYSTEM Filed Aug. 2o, 1936 4sheets-sheet s QMWW y A TURA/EV Dec. 20, 1938. E. P. G; WRIGHT Er Al.

TELEPHONE SYSTEM Patented Dec. 20, 1938 UNITED STATES PATENT OFFICETELEPHONE SYSTEM Esmond P. G. Wright,

George C. Hartley, and

Application August 20, 1936, Serial No. 96,924 In Great BritainSeptember 3, 1935 17 Claims.

This invention relates to telephone systems and particularly to systemscomprising automatic switching equipment for completing desiredconnections.

It is the object of the invention to increase the flexibility andeiiiciency of automatic switching equipment in telephone systems.

In telephone systems comprising automatic switches for establishingdesired connections, it is known to provide digit registering andtranslating meansv for controlling the operation of switches throughwhich a desired connection may be established.

A feature of the invention is the provision of means in a telephonesystem comprising automatic selector switches for translating theposition to which a selector switch, through which the establishment ofa desired connection is attempted, into the code of an alternative routefor use in controlling the reoperation of this switch and the operationof such other switches as may be included in the alternative route.

Another feature of the invention is the connection of a register switchto a selector which has encountered an all-trunks busy condition and theadvance of the register switch to a position dependent upon the identityof the trunk group in which all trunks were found busy. If the selectoris a two-digit switch the register switch is first advanced to a levelcorresponding to the level of the selector in which the selected trunkgroup is located; and then the register switch and the selector switchare advanced step by step in synchronism in these levels until theselector switch reaches its ultimate off-normal position,

whereby the position of the register switch indicates the identity ofthe busy trunk group.

The invention and its features will be better .understood byconsid-ering in detail a multiofce telephone system in which theinvention is embodied, one such embodiment being representedschematically in Figs. 1, 2 and 3 of the drawings which form a part ofthis specification and another embodiment being representedschematically in Figs. 4 and 5 of the drawings.

The invention may be applied to the selector and switch controllingdevices of other systems by any one skilled in the art. Referring to thedrawings: Fig. 1 shows a two-digit two-motion se-A lector OS;

Fig. 2 shows the register switch VR of a special translator and .a nderswitch F for connecting the translator to any one of a group ofselectors;

Fig. 3 shows a portion of a translating switch designation distinguisheseach contact spring of a relay or magnet from the other contact springsof the same element.

The outgoing group selector of Fig. 1 comprises a vertical magnet VM,rotary magnet RM, release magnet ZM, a Vertical commutator VW, aterminal bank and two sets of brushes; one set consisting of brushes -I,-l-I, and Pl and the other set consisting of brushes 2, +2, and P2. Thisselector is adapted to be selected and seized, if idle, by a rstselector which is set in accordance vwith the rst of three oce codedigits transmitted by a register-translator, neither the first selectornor the register-translator being shown in the drawings. After seizurethe selector of Fig. 1 is operated under the control of the second digittransmitted by said register-translator to select a level of theterminal bank and by the third digit transmitted by theregister-translator to select the desired group of terminals in theselected level. The selector of Fig. 1 thereupon hunts for an idle setof terminals in the selected group and extends the connection over thejunction connected to this set of terminals to the called ofce orexchange. If no junction is available, the brushes are stopped on thelast set of terminals in the selected group and in certain cases, it ispossible to route the call over a different group of junctions toanother oiiice and through this other oiiice to the desired exchange.The completion of a call over an alternative tandem route is desirable,of course, only when all of the direct junctions to the called exchangeare busy.

The reoperation of a selector switch OS to select an alternative groupof junctions is controlled by the special translator shown in Figs. 2and 3. The finder switch F comprises a magnet FM, a set of brushes fml,fm2, fm3, fmll, fm5 and fm, and a bank of terminals to which are.connected one or more groups of outgoing group selectors OS. Thespecialtranslator comprises a register switch VR and a translator switchTS. The register switch has a vertical magnet VMZ, a rotary magnet RM?,a vertical commutator, a terminal bank and brushes wml and mm2. Thesegments of the vertical commutator of the register switch are connectedto the corresponding segments of the vertical commutators of all theselectors OS to which the translator is common.

The translator switch TS shown in Fig. 3 is of the kind described inPatent 1,900,969, granted to E. P. G. Wright, March lll, 1933 and inPatent 1,903,019, granted to E. P, G. Wright et al., March 28, 1933.Each level of the translator switch is connected to a position of theregister switch of Fig. 2, which position represents the translatedcharacteristics of a group of direct junctions for which there is analternative route.

The operation of selector OS and the operation of the specialtranslator, in consequence of of the selector OS nding all junctions ina desired group busy, will be described in detail. When a subscribermakes an `outgoing call, the digits dialed are received by aregister-translator which transmits three code digits, the rst of whichsets a iirst code selector, and the second and third of which set atwo-digit outgoing selector OS of Fig. l. When the outgoing groupselector OS is seized by a rst selector (not shown), relay A is operatedin a circuit from battery through its right winding, back contacts ofsprings hs, hb2, haZ and cl3 over the conductor incoming from the firstselector, through the controlling register-translator (not shown), backover the conductor, back contacts of springs el, hat, M33, hs, and leftwinding of relay A to ground. Relay A closes a circuit at the frontcontact of spring al for operating relay B; and relay B closes a circuitfor operating relay C from the winding of relay C, vertical olfnormalcontact n2, rotary off-normal contact 1112, contacts b3, ha and hb5rtoground. Relay A is alternately released and reoperated in response tothe impulses of the second code digit when transmitted by theregister-translator. Each release of relay A closes at the back contactof spring al a circuit for energizing the left winding of relay C andthe winding of vertical magnet VM, thereby raising the brushes of theswitch up to the level corresponding to the digit transmitted. Beingslow in releasing, relay B remains operated during the response of relayA to each digit received. The circuit for operating relay C is opened atcontact 112 when the switch moves out of normal position but relay C isheld by its left winding until all of the impulses of the second codedigit have been received by relay A. The release of relay C closes acircuit through the winding of relay E, contact nl, back contact ofspring c4, rotary off-normal contact m2, contacts b3, ha5 and hb toground. Relay E operates, transferring at spring e5 the left winding ofrelay C from magnet VM to magnet RM and closing at contact c3 a circuitfor reoperating relay C. At spring c, relay C opens the operatingcircuit and closes a locking circuit for relay E. Relay A then respondsto the impulses of the third code digit when transmitted from theregister-translator, each release of relay A closing the circuit foroperating magnet RM, the brushes being thereby advanced by magnet RMinto engagement with the first set of terminals in the desired group ofthe selected level. When the brushes are advanced out of the normalrotary position opposite the selected level, the rotary oli-normalsprings are actuated, contact n12 being eiective to hold open theoperating circuit for relay E. When all of the impulses for the thirdcode digit have been received, relays C and E are released insuccession. While relay E is releasing, the first two sets of terminalsin the selected group are tested. If the set engaged by the upper set ofbrushes is idle, relay I-IA is operated by the current in a circuit fromground through contact bl, vertical offnormal contact n3, back contactof spring hbi, winding of relay HA, rotary off-normal contact nrl,contact cl, front contact of spring e4, contact hsl and through theright winding of relay G to battery. Relay G is marginal and does notoperate at this time. Relay HA closes a locking circuit through itscontact hal; and, at its front Contact had, connects ground from contactbi to the test brush Pi to guard the selected junction from seizure byany other hunting selector. The operation of relay HA extends theconnection from the first selector through the iront contacts'of springsmi2 and m3, and through brushes l and -2 to the junction connected tothe terminals with which these brushes are in engagement. The opening ofcontact ha prevents the reoperation of magnet RM after relay E releases.

If the set of terminals engaged by the upper set of brushes is busy, butthe set of terminals engaged by the lower set of brushes is idle, thebusy ground potential encountered on the test terminal with which brushPl is in engagement is effective by its connection through the backcontact of spring hall and contact b4 to shortcircuit the winding ofrelay HA so that relay HA does not operate and relay G operates. Relay Gcloses a locking circuit from battery through contact gil, left windingof relay G, contact g2, front Contact of spring b5, Vertical off-normalcontact c5, and contacts ha and M15 to ground. With relay HA normal andrelay G operated, a circuit is closed for operating relay HB; thiscircuit is traced from battery through the winding of relay HB, backcontact of the eleventh step spring sl, conta-cts g5, n3 and bl toground. Relay HB locks through the front contact of its spring kbl; andthe opening of the back contact of this spring prevents the operation ofrelay HA when relay E releases. Relay G releases when relay HB opcrates.V/ith relay HA normal and relay HB operated, the connection from theiirst selector is extended through the back contacts of springs haZ andhat and the front contacts of springs hb2 and hb, and through thebrushes 2 and +2 to the junction connected to the terminals with whichthese brushes are engaged. The operation of either of relays HA or HBcauses the release of relay A and the release of relay A causes therelease of relay B, the ground potential for holding whichever one ofrelays HA or HB is operated being supplied from the seized junctionthrough the brush PI or 1LT-'Zas the case may be. Theregister-translator controls the operation of the remaining switchesrequired for completing the ydesired connection. When the connection isreleased, the disconnection of the holding ground potential from thetest conductor P causes the release of relay HA or HB and operation ofrelease magnet ZM in a circuit through the back contact of spring b5,Vertical oil-normal contact p5, and back contacts ha and hb. When theswitch reaches normal the circuit for operating magnet ZM is opened atcontact fc5.

If both sets of contacts, with which the upper and lower sets of brushesare in engagement, are busy when relay C releases at the end of thegroup selecting operation of magnet RM, the ground potential encounteredA'by brush P2 is connected through the back contact of spring hb4 andcontact g4 to short-circuit the Winding and thereby prevent theoperation of relay HB. The operating circuit through the right windingof relay G having been opened by the release of relay E and the leftwinding of relay G- being short-circuited by the busy ground potentialencountered by brush P2, relay G releases closing a circuit foroperating the rotary magnet RM; this circuit is traced through contactel, the back contact of spring hs'l, contact gl, rotary oil"- normalcontact M2, and contacts b3, ha5 and hb to ground. The operation ofmagnet RM steps the brushes to the next sets of terminals in the groupwhich are tested in the manner hereinbefore described,'except that thetest circuit through the right winding of relay G is closed through thecontact rml while magnet RM is releasing instead of through the frontcontact of spring c4. The selector' is provided with an additional brushD and associated terminals for use in determining Whenever the brushesare advanced to the last terminal of a group without iinding any line inthe group idle. To this end the contact g3 ci relay G is connected toeach of the terminals in the selected level with which brush D engageswhen advanced to the last position of a group; so that, if all of thejunctions in a selected group are busy, a circuit is closed from thebusy ground potential encountered by brush P2, through the back contactof spring hbd, contact g3, terminal and brush D, contact c2, and lowerwinding of relay HS. Relay ES operates and closes at its contact hsli alocking circuit through its upper winding, the front contact of springb5, contacts p5, hai and hb to ground. Relay G releases but the circuitthrough contact gly for reoperating magnet RM is held open at the backcontact of spring hs'l. At contacts-7135 and het the connection of theincoming conductors and -lto the windings of relay A is'interchanged soas to reverse the current over these conductors and through theregister-translator which in known manner thereupon stops thetransmission of digit impulses until the normal direction oi current isrestored.

All of the junctions in the selected group having been found busy andrelay HS operated, a start circuit is closed for initiating theoperation of the finders of all idle special translators in order thatone of these translators be associated with the selector OS in question.This start circuit J's traced from Ibattery through contact hs3 and overconductors S, through the off-normal contact nl and contact b of relayB2 of each idle translator, to the upper Winding of the start relay STof each such translator. Relay ST closes a circuit from battery throughthe winding of finder magnet FM, contact st2, back contact of spring p2and back contact of spring d2 to ground. The brushes of the iinder ofeach idle translator are thereby advanced to hunt for the selector OSwhich has found all junctions in a selected group busy. When theterminals, to which this selector is connected, are found by one of thehunting switches, relay P2y of the iinder switch in question is operatedby the current in a circuit from ground through contact stl, lowerwinding of relay P2, brush fml and terminal, over conductor T andthrough contact hs3 of the selector in question to battery. At contactpl, ground is connected through the upper winding of relay P2 to theterminal with which brush fml is in engagement, the potential of thisterminal being reduced sufficiently to prevent the operation of therelay P2 of any other hunting nder switch. At the back contact of springp2, the circuit for operating magnet FM is opened to stop the finderswitch and at the iront contact of spring p2 a circuit is closed throughthe lower winding oi relay T and resistor BSP. This resistor is commonto all of the translators so that the current through the' lower windingof relay T will be insufficient to cause the operation of this relay ifthere is any other translator in the same group then connected to one ofthe selectors OS and making use of the common marking multiple betweenthe ybanks of the selectors and the banks of the register switches VR.This marking multiple need not necessarily be a straight multiple.Assuming the multiple to be free, relay T operates and at its contact tlconnects its upper winding in parallel with its operating windingthereby increasing the drop in potential through resistor BSP to preventthe operation of the T relay of any other translator in the group. Atcontact t3 a circuit is closed through the lower winding of relay B2 toground at contact d3, but this winding is sho-rt-circuited as long ascontacts MS are closed. The interruptor contacts MS are opened andclosed 10 times per second; and the next opening of these contacts,after relay T operates, causes the operation of relay B2. Relay B2 opensthe operating circuit for relay ST at contact h6; but it also closes alocking circuit through the lower winding and Contact stt of relay ST,back contact of spring ci, to ground at contact b3. The actuation ofcontact spring b2 transfers the interrupter contacts MS through thefront contact of spring std to the winding of vertical stepping magnetVM2; and theoperation of this magnet each time contacts MS are closedraises the brushes of switch VR one step. When the level correspondingto that on which the brushes of switch OS are standing is reached, acircuit is closed from ground at contact t4 through the Winding of relayC2, vertical comrnutator brush or and segment, through the correspondingsegment and the brush VW of the vertical commutator of selector OS inFig- 1, back contact of spring eli, conductor L, terminal and brush fm2of the finder F, and through contact t2 to battery. Relay C2 is operatedby the current in this circuit. At its back contact spring cl opens thecircuit through the lower winding of relay ST and at its front contactconnects this winding through the front contact of spring b2,interrupter contacts MS, contact t3, and the back contact of spring d3to ground; and the next opening of the interrupter contacts MS causesthe release of relay ST. The opening of the front contact of spring stflprevents the further operation of magnet VM2 and the closing of the backcontact of spring stil connects the winding of relay A2 to theinterruptor contacts MS. Relay A is then alternately operated andreleased under the control of contacts MS. Each operation of relay Acloses, at the front contact of spring a3, a circuit for energizingmagnet RME and., at its contact al, a circuit from ground on theterminal with which brush fmt is engaged, through contact g2, brush jmd,over conductor R tothe selector OS, front contact of spring hs'l,contact el and through the winding of rotary magnet RM to battery. Thusthe rotary magnet RM2 of the register switch VR of the translator androtary magnet RM of the selector OS are simultaneously alternatelyoperated and released, under the control of relay A and interrupter conltacts MS, to advance the brushes of each of these switches step-by-step.When the brushes of selector OS reach their eleventh rotary position,the contact springs si, s2 and s3 are actuated. At the back contact ofspring s2, the short circuit around the left winding of relay EL isopened and, the contact i152 being closed, relay EL operates. Theoperation of relay EL causes the release of relay C2, disconnects theand conductors incoming from the first selector from the windings ofrelay A, and closes a circuit from battery through contact t2 of relay Tin the translator, brush fm2, conductor L, front contact of spring el l,conductor to the first selector and register translator, back over theconductor, through contact elfi and the right winding of relay EL toground. Relay EL is thus held operated and the register-translator isthus maintained inert. At the front contacts of springs cl3 and elfi thewindings of relay A are connected over conductors and -l-, throughbrushes fm and fm, and contacts a2 and b4 of relays A2 and B2, in serieswith the upper winding of relay D2, the contact a2 being closed as soonas springs MS are opened and relay A2 releases. Relay D2 is operated bythe current through Yits upper winding, and locks through its lowerwinding and contact d5 to ground at contact b3. The opening of contactd3 prevents the further operation of relay A2 and magnets RM2 and RM,the brushes of switch VR having been advanced to a positioncomplementary to that of the junction group in which all junctions werefound to be busy. After relay D2 operates, relay B2 is held operated byits upper winding in a circuit through its contact bi, back contact ofspring gl and through the front contact of spring d2. At contact cl2,relay EL closes a circuit for operating the release magnet ZM of switchOS; this circuit is traced through contacts cl2, hsll, front contact ofspring b5 of relay B, and through contacts p5, ha and hb to ground. Whenthe selector switch reaches normal, the opening of contacts n causes therelease of relay HS and magnet ZM. Relay A of the selector is heldoperated over the and -lconductors, through brushes fm and fmS, andthrough contacts c2 and dit in the translator, the upper winding ofrelay D2 being short-circuited iby Contact dd. The register switch VRhaving been set to a position indicative of the group in which theselector OS found all junctions busy, the marking multiple between thevertical commutators of the translators and selectors may be releasedfor use by other translators and selectors; to this end the circuitthrough the winding of relay T is opened at the back contact of springd2, and relay T releases.

With the register switch VR set in a position indicative of thecharacter of the group in which selector OS found all junctions busy,the winding of relay F2 is connected through contact d, brush Uml andterminal, over the S conductor by which this terminal is connected torelay TA of the translating switch in Fig. 3, through the winding ofrelay TA, to the normal terminal of the group with which brush tmf!engages. If the translator is then idle, the brush tm is in engagementwith its normal terminal and relays` F2 and TA are operated. Relay F2closes a circuit through the front contact of its spring f3 and thefront contact of spring b5 for operating relay G2. Relay TA closes acircuit at contact tal for operating relay TC and as soon as theinterrupter contacts MS of the translating switch are next opened relayTC operates. Contact spring tcl transfers the interrupter contacts MS tothe winding of the translating switch magnet TM and contact tc3 closes alocking circuit for relay TC. If desired, metering relays D3 may beconnected to the S conductors from the bank of switch VR in series withrelay TA. The particular D3 relay, which is included in this circuit foroperating relay TA, operates; and the aforementioned operation of relayTC closes a circuit through contact dl for operating that one of aplurality of overflow meters OM, which is individual to the junctiongroup in which all junctions were found busy. The interrupter contactsIS and MS operate in synchronism, the contacts MS being effective toalternately operate and release the translator stepping magnet TM. Thecontacts iS are connected to all of the translator switch brushes tml,tm2, tm3, the banks of which are multipled to impulse conductors P,leading to the terminals of the bank of switch VR with which brush mm2engages. Translated codes are thus obtained for the groups of junctionsconnected to the bank of switch OS, which codes control the switchingoperations required for reaching the same offices over alternativeroutes. For a more complete description of the interconnection of theterminals of the bank of switch VR over conductors P to the terminals ofswitch TS to give the desired translated codes, reference may be had tothe aforementioned Wright Patent No. 1,900,969. The operation of magnetTM under the control of contacts MS advances the brushes of switch TS totransmit the particular alternative route code identified by the settingof switch VR. Relays TA and F2 are released when brush tmll leaves thehome position. Relay G2 is held operated through the back contact ofspring f3, contacts g5, d5 and the front contact of spring g4. YRelay B2releases when contact f4 is opened. Each time one o-f the translatorbrushes tml, tm2 or fm2 encounters a terminal to which the conductor P(from the terminal in the bank of switch VR with which the brush mm2 isin engagement and which identies the junction group in which alljunctions were found busy) is multipled, the winding of relay A2 isconnected through the front contact of spring g3, contact fl, brush mm2and terminal, over a conductor P, terminal and brush tml, tmZ or tm3, tothe interrupter contacts IS. As soon thereafter as these contacts areagain closed, relay A2 is operated, the opening of its contact a2causing the release of relay A of the selector OS. Switch TS steps onthe back stroke of magnet TM so that the stepping does not affect thecontrol of relay A2 by contacts IS. The impulses corresponding to thefirst and second digits of the alternative route code are thustransmitted to relay A2 and through it to relay A of selector OS tooperate the vertical magnet VM and rotary magnet RM and thereby againadvance the brushes of switch OS to the rst set of terminals in thealternative route group in the manner hereinbefore described. When anidle tandem junction in this group is found, relay HA or relay HBoperates extending the connection to the selected junction. Theremaining code digits are then sent from the special translator by thecontacts a2 of relay A of the translator to control the operation of oneor more selectors in the tandem or intermediate exchange or exchanges.When all of the code digits, necessary to reach the desired exchange,have been transmitted, re-

lay TB is energized in a circuit through one of the translator brushesand an engaged terminal, which terminal marks the end of a translatedcode, and through contacts IS to ground. At contact tb2 the winding ofmagnet TM is connected in parallel with the winding of relay TB. I'heopening of the back contact of spring tbl causes the release of relayTC. After relay TC releases, relay TB is held through contact to2 andthrough the ofi-normal terminals with which brush tmll engages until theswitch TS is restored to normal. The stepping magnet TM operates throughits own interrupting contacts, and through contacts tbZ and to2 to theground on brush im@ When the switch reaches the home position relay TBreleases and magnet TM.can not reoperate. While relay TB is operated,ground is connected through the front contact of spring tbl overconductor S to the terminal with which brush crm! is in engagement,thence through brush wml and contact dii to the winding of relay F2causing the reoperation of relay F2. The operation of relay F2 causesthe release of relay G2. The release of relay G2 causes the release ofrelay D2 and the release of relay D2 causes the release of relay F2.With relays B2, F2 and G2 released the release magnet ZM2 is operatedand the register switch VR is restored to normal in usual manner. Therelease magnet ZM releases when the switch reaches normal and contactsn2 are opened.

'I'he aforementioned release of relay D2 opens at its contact dl theabove-mentioned circuit through the register-translator and rightwinding of relay EL of the selector OS. The release of relay ELcompletes at the `back contacts of springs cl3 and cls the connectionfrom the iirst selector and register translator, through the brushes ofselector OS to the seized junction and through the tandem ofce to thedesired office. The register-translator thereupon controls thecompletion of the desired connection in usual manner.

It may be desirable to connect more than one group of selectors OS, tothe nder switches of argroup of translators in which case it is thendesirable that there be no interference between the two groups incontrolling the setting of the register switch VR. To this end the relayE2 may be provided in which case ground is directly connected to theterminals engaged by brush fm3 and which are associated with theselectors of one group; but the terminals with which brush fm3 engagesand associated with the other selector group are not connected directlyto ground. When a selector of the second group calls in an alternativeroute translator the rst operation of relay A2, while effective tooperate magnet RM2 and advance switch VR one step, is ineiTective tooperate magnet RM of the selector because the terminal with which brushfmS is in engagement is not connected to ground. When relay A2 releasesafter switch VR takes the lirst rotary step, the closing of the rotaryoi-normal springs arl causes the operation of relay E2; the circuit forrelay E2 is traced through the back contact of spring c2, contact ml,and back contacts of springs a3 and gl. Relay E2 locks through contactse2 and b3. At contact el, ground is connected to Contact al so that eachsucceeding operation of relay A2 causes the operation of magnet RM ofthe selector as well as the operation of magnet RME of switch VR. Theswitch VR is thus given one more step when the associated selector is inone group than when it is in the other for the same position of theselectors and the possibility of interference between the two -groups isthereby minimized.

On certain routes, such as a group of long distance lines of a characterwhich provides high grade transmission, it is undesirable to providealternative trunking. In such a case, the selector is redirected und-erthe control of the special translator to a level in which the brusheswill be automatically advanced eleven steps to the eleventh rotaryposition in which position contact springs Si, S2 and S3 are againactuated. The special translator is released and the selectorreconnected to the register-translator to indicate the busy condition,whereupon release again takes place as hereinbefore described.

Consider now the embodiment of the invention illustrated in Figs. 4 and5. In this system two digits determine the exchange in which a wantedsubscriber is located. A calling subscribers line is connected to ai'irst selector which in response to the first digit dialed selects anidle second selector. The second selector is a onedigit selector and, inresponse to the second digit dialed, selected a group of junctionsoutgoing to the wanted exchange and selects an idle junction in thisgroup. One of these second selectors OS is represented in Fig. 4, onlythe apparatus required for a disclosure of the invention being shown.With each group of 25 second selectors, there is associated a group ofthree link circuits one of which is shown in Fig. 4. Each link comprisesa selector finder switch SF having access to 25 second selectors and aregister finder RF having access to a group of 5 or 6register-translators RC, the translators being common to all of thelinks in the exchange. When a second selector findsY all junctions busyin a selected group it calls into service a link and a translator whichthereupon assumes control of the rerouting of the call and which alsoreceives and registers the numerical digits dialed by the callingsubscriber. The second selector is released from its set position and isselectively reoperated to seize an idle junction to a tandem exchange.This translator then controls switching operations in the tandemvexchange to select an idle junction leading to the called exchange andthe numerical selections in the called exchange.

When a second selector is seized and, in response to the second digitdialed by the calling subscriber, is moved out of normal, the off-normalcontact n2 closes and relay X operates in series with the release magnetZMl. The release magnet is marginal and does not operate in series withrelay X. At contact :rl a circuit is closed for operating the commonstart relay SA. At contact sa, relay SA closes circuits for operatingrelay ST4 of each free link in the group associated with the group ofsecond selectors to which relay SA is common. In each suchlink relay ST4closes, at Contact StZ, a circuit for operating the selector-iindermagnet SEM. When the brushes of a nder engage the terminals to which theselector OSA is connected, a circuit is closed through brush sfml andboth windings of relay P4 to 4ground at contact sti.` Relay P4 operatesand at its contact p2 short-circuits its right winding, therebydecreasing the potential of the terminal with which brush sfml is engaged to cause the release of relay SA and thereby stop the hunting ofthe other links. In the successful link, the operation of relay P4 opensthe operating circuit of magnet SFM and at the front contact of springpl closes a circuit for operating relay PP. At contact m05, relay PPopens the operating circuit of relay ST4. At the front contact of springppll, relay PP closes a circuit for operating the finder magnet RFM;this circuit includes the back contact of spring t2, brush rfmi of theregister-lnder switch and the back contact on! of anyregister-translator with the terminals of which the brushes of switch RFare then in engagement. If this translator is busy, the ON relay is notoperated and the magnet RFM is energized to step the brushes to the nextset of terminals. When the brushes encounter a set oi terminals to Whichan idle translator is connected, the ON relay of this translator beingoperated, contact oni is open and magnet RFM cannot reoperate; and thehunting operation is ended.

If the second selector OS@ finds an idle junction in the selected group,the operation of the usual switching relay H, the winding of which isnot shown in the drawings, opens at contact hl the operating circuit ofrelay X. The release of relay X causes the release of relay Pl!- of theassociated link and the translator is not brought into action.

If. however, the selector finds all of the junctions in the selectedgroup busy and the level of this group is one arranged for alternativerouting, the eleventh step springs are actuated when the brushes reachthe eleventh rotary position. The operating circuit for relay X isopened at contacts s2, and a circuit is closed from ground at contactbl, through the oir-normal springs nl, eleventh rotary step spring sl,winding of relay K, and through brush sfm and contact ppl of relay PP ofthe associated link. Relay K operates in this circuit; locks through itscontact k2; and closes, at its contact kl, a circuit through brush sfmZ,contact ppl of relay PP of the link, winding of relay Til, front contactof spring ppl and winding of magnet RFM. Being marginal magnet RFM doesnot reoperate, but relay T4 operates. Relay T4 closes a holding circuitfor relay PP through contacts mit and il, and through brush rfm toground at the back contact Tl of relay R of the associated translator.Relay P4 of the link releases when relay X of the selector is released.Since relays P4 and PP of the link are slow in releasing, the abovetraced holding circuit for relay PP is closed soon enough to prevent therelease of this relay. The aforementioned operation of relay K opens vatcontacts 7c3 and 74:4 the normal connection between the incoming andconductors and relay A4 of the selector OSG; but relay All remainsconnected tothe calling loop through brushes sfm and sfm'i, contacts mi2and m23, back contacts of springs t3 and t4 and brushes smil and sfm'until relay T5 operates. Relay Til interconnects the selector andregister-translator, the calling subscribers loop being disconnectedfrom the windings of relay All and connected through the front contactsof springs t3 and t4 and brushes rfm and Tfn/:3 to the windings of relayRA in the register-translator. Relay A6 is held operated throughcontacts t5 and t5, brushes rfml and #m5, back contact of spring T2 ofrelay R in the register-translator, contact 80.2 and through contacts mfand m95 in parallel. Relay RA operates over the calling subscribersloop, closing at the front contact Vof spring ral a circuit foroperating relay RB; and relay RB closes at contact Th2 a circuit foroperating relay BB. The opening of contact T123 causes the release ofrelay ON. The closing o contact on! connects ground to the terminal withwhich brush 'rfml is in engagement, through the front contact of springt2 in the link, to the winding of relay T4 to hold relay T4 operatedindependent of the ground potential on the sleeve conductor P ofselector OS. Relay BB of the translator completes a circuit foroperating relay MG from the common resistor BS in the link, throughContact t9 and brush rfm, contact bbS of relay BB, contact mja andthrough both windings of relay MG in series. Relay MG operates if the MGrelay of none of the other translators is operated when relay BB of thetranslator in question operates. At contact mgl, the high resistanceright winding is short-circuited to increase the drop in potentialthrough resistor BS and thereby prevent the operation of the MG relay ofany other translator while the common marking multiple between thevertical commutators of the selectors and the banks of register switchesBS of the translators is in use by the translator whose operation isbeing described. Relay MG closes the operating circuit of theselfinterrupting stepping magnet BSM of switch BS through contact m93,back contact of springs mi and mf to ground at the front contact ofspring bbl. Each of the groups of terminals with which brush bsml ofswitch BS engages, is connected by a common marking multiple to thecommutators of the selectors in a different group of second selectors;and when brush bsml engages the terminal which is connected to thecommutator segment with which brush-es vm of the second selector inquestion are in engagement, relay M of the translator operates, theopening of the back contact of spring ml'preventing the further advanceof switch BS; the circuit for operating relay M is traced throughcontact myZ, brush bsml, common' marking multiple conductor, commutatorwipers um of selector OS4, brush smil of switch SF, contact t8 of linkrelay T, brush Tfm of switch RF, to ground at contact mg of relay MG ofthe translator. At the front contact of spring m! relay M closes acircuit for operating relay MF; and relay MF locks through the frontcontact of its spring mfG, to ground at contact bbl. Both of contactsmf2 and m95 having been opened, relay A4 of selector OS4 releases,causing the release of relay B (winding not shown). The release magnetZM4 is thereupon operated through contacts n2, b2, al and hl, thebrushes of selector OS4 being thereby restored to normal. Relay M of thetranslator releases when the selector is restored. Relay MF having beenoperated and relay M released, both of contacts mf3 and m2 are open andrelay MG releases. The common marking multiple between the secondselectors and switches BS of the translators is thereby released.

rThe release of relay MG closes, at contact m95, the above describedcircuit through brushes rfmd and Tfr/"L5 for operating relay All ofselector OS4. The release of relay MG also closes a circuit through thewinding of relay CC and Contact r3, myd, se'and mfd; and, as soon afterthis circuit is closed as the interrupter contacts MS are opened, relayCC' operates. At the front contact o spring cci, the winding of steppingmagnet SSM of switch SS is connected to the interrupter contacts MS,which contacts are opened and closed ten times per second. Eachoperation of magnet SSM advances the brushes ssml, ssmZ and ssm3. Whenbrush ssm3 engages 'terminal 4, a circuit is closed through this brushand contacts mf and sa for operating relay SA. Relay SA is held in thiscircuit until relay SZ operates during the next 11 additional steps ofswitch SS. At contact sa2, relay SA opens the short circuit aroundimpulse springs. IS, which springs are also opened and closed ten timesper second. Each opening of springs IS, after contact 8d2 is opened,causes the release of relay A4 of selector OS4, the brushes of thisselector being raised onev step by each operation of relay A4 in usualand well-known manner. Assume that the tandem office junctions, whichconstitute the route alternative to the group in which the selector OS4found all junctions busy,

are located in the sixth level of the bank, so that the brushes are tobe raised to the sixth level by the operation of relay A4 under thecontrol of springs IS. In this case the terminal, with which brush scm3of switch SC is in engagement when in normal position, is connected tothe terminal with which brush sSmZ of switch SS is in engagement in thetenth off-normal position. Six impulses having at that time been sent torelay A4, a circuit is closed from ground at the front contact of springmfl, through brush scm3 and normal terminal, terminal Ill and brushssmi, contact sal, and lower winding of relay SZ. Relay SZ locks throughcontact S24 and brush ssml; and contact S22 of relay SZ shortcircuitsthe impulse springs IS to prevent the transmission of another impulse torelay A4.

'Ihe selector OS4 thereupon hunts in the sixth 'contact S25, the magnetSSM is connected to brush ssml and the brushes of switch SS are thusadvanced to normal; and at contact S21 a circuit for operating steppingmagnet SCM of switch SC is closed. When switch SS reaches normal, relaySZ releases and opens the operating circuit of magnet SCM; the releaseof magnet SCM advances the brushes scml, scm2 and scm3 to the rstoff-normal position. Relay CC reoperates when relay SZ releases and thecontacts MS are next opened; and thestepping magnet SSM is energizedeach time contacts MS are closed to again advance the brushes of switchSS. Relay SA reoperates when position 4 is reached and is held untilrelay SZ operates during the next 11 additional steps. The selections tobe controlled in the tandem oiiice determine the digits transmitted bycontacts IS to the tandem oiiice, an impulse being transmitted by eachclosure of these contacts after contact sal is opened by the reoperationof relay SA. The rst off-normal terminal, with which terminal brush scm3is in engagement is connected to brush bsmZ and through cross connectingconductors CCF to the desired one of terminals 4 to I3, inclusive, withwhich brush ssm2 engages; and, when brush ss'mZ encounters theparticular terminal which is connected to the terminal with which brushbsmZ is in engagement, relay SZ is reoperated to end 'the first train ofdigit impulses being transmitted to the tandem ofce. Relay SZ causesswitch SC to be advanced to the second off-normal position and a seconddigit is sent to the tandem oflice in the same manner, the circuit foroperating relay SZ a third time to end the second digit transmitted tothe tandem olice being traced through brush scm3 and second oir-normalterminal, brush bsm3 and terminal with which it is in engagement, overone of cross connecting conductors CCF to the terminal with which brushssm2 is then in engagement and through contact sal, to the lower windingof relay SZ.

When all selections necessary to reach the wanted exchange have beentransmitted from the translator, the further progress of the calldepends upon the numerical digits dialed by the calling subscriber; andduring the transmission of the oiiice code digits and wholly independentthereof, these numerical digits have been received by relay RA andregistered by switches MS, HS, TS and US. Each release of relay RA inresponse to the impulses of the thousands digit closes a circuit fromground through the back contact of spring ral, contacts rb'l andr4,winding of relay C5, brush d`d`3 in normal position, to stepping magnetMSM of the thousands register switch. Relay C5 operates in sc ries withthe stepping magnet and being slow in releasing remains operated untilall of the impulses in the train created by the dialing of the thousandsdigit have been received by relay RA. Relay C5 closes a circuit atcontact cI for operating stepping magnet DDM of switch DD. When relay C5releases at the end of the digit, magnet DDM releases thereby advancingthe brushes ddl, dd2 and dd3 to the iirst off-normal set of terminals.In response to the hundreds digit, relay RA is effective to operate thestepping magnet HSM of the hundreds register through brush dd3 andterminal I; in response to the tens digit, relay RA is effective tooperate the stepping magnet TSM of the tens register through brush dd3and terminal 2; and in response to the units digit, relay RA iseffective to operate the stepping magnet USM of the units registerthrough brush dd3 and terminal 3. At the end of the units digit, therelease of relay C5 again causes the release of magnet DDM and thebrushes of switch DD are advanced to the fourth off-normal position andno additional impulses will be registered. The numerical digits may besent out as soon as they are registered and the preceding digit has beensent. that the thousands digit will not be sent until completelyreceived, relay SZ is held operated, after the second digit has beentransmitted to the tandem ofce, until switch DD has advanced out ofnormal position; the circuit for holding In order` relay SZ Vis tracedthrough its upper winding and contact sal, brush scmZ in secondoi-normal position, brush' ddmZ in normal position to ground at thefront contact of spring bb. In like manner relay SZ is held throughbrush scm2 in ofi-normal positions 3, 4 and 5 and brush dd2 inoff-normal positions I, 2 and 3 so that each of the hundreds, tens andunits digits must have been completely received before it can betransmitted -to the called exchange. The sending switch SS isreoperated, as hereinbefore described to send each one of the numericaldigits, the circuitl for operating relay SZ to end the thousands digitbeing traced through contact sal, brush ssm2, the cross-connectingmultiple se, terminal with'which brush msm? is in engagement, vand brushscm3 lin third oit-normal position; Yto endv the sending ofthe hundredsdigit, the circuitI for operating relay SZ includes brush scm3 in fourthoff-normal position and the terminal with which brush hsm2 is inengagement; to end the sending of the tens digit, the circuit foroperating relay SZ includes brush scm3 in fifth off-normal position andthe terminal with which brush tsm2 is in engagement; and to end thesending of the units digit, the c'puit for operating relay SZ includesbrush scm in sixth off-normal position and the terminal with which brushusmZ is in engagement.

When the units digit has been received and transmitted, the operation ofrelay SZ closes at contact ssl the' circuit for operating magnet SCMwhereby switch SC is stepped to the seventh oil-normal position, inwhich position relay R is operated by the energization of its lowerwinding, through brush scmB in the seventh oiT-normal position to groundat the front contact of spring mfl. The operation of relay R causes therelease of relay PP of the link; and the release of relay PP causes therelease of relay K of the selector OS4 and the release of relay T4 ofthe link. Relay K releases quickly and relay T4 releases slowly. Whenrelay K releases, the calling subscribers loop is connected throughcontacts k3 and 104 to the brushes (not shown) of the selector OS4 thuscompleting the connection between the calling and called lines. Whenrelay T4 releases, the opening of contacts t3 and t4 disconnects thecalling line from relay RA. After relay PP releases and before relay Treleases, the resistor which is normally short-circuted by contact r2 ofrelay R is connected in the loop across contacts t5 and t6 so that therelease of relay K will not cause excessive noise at the callingstation. The release of relay RA causes the release of relays RB, BB andMF in succession. Switches MS, HS, TS, US, SS, SC and DD are thereuponadvanced to normal by operation of their stepping magnets throughbrushes msml hsml, tsml, usml, ssml, scm! and ddl respectively. SwitchBS is a non-restoring switch. When all of the numerical registerswitches are normal, relay ON reoperates and opens at contact o'rLZ aholding circuit for relay R. Contact o'fLl disconnects ground from theterminal with which brush Tfml of nder RF is in engagement, therebycausing this register-translator to test idle.

If a selector OS4 is advanced into the eleventh rotary position on alevel for which there is no alternative route, the link is seized whilethe selector is being stepped up to this level and theregister-translator is seized when the eleventh rotary stop springs areactuated as hereinbefore described. Relay MG operates and switch BShunts for the level to which the brushes of switch OS4 have been set.'Ihe vertical commutator segments of all levels for which alternativeroutes are not provided are connected to one terminal of the bank withwhich brush bsml engages. When brush bsml encounters this terminal,relays M and MF are operated as hereinbefore described. No alternativeroute translation being required, relay R is immediately operated, whenrelay MF operates, in a circuit through brush bsmd in normal position toground at contact mfl. The operation o f relay CC is thus prevented bythe opening of contact T3 so that no digits can be transmitted. RelaysPP and T4 of the link and relay K of the selector are released ashereinbefore described. Upon release of relay K, a busy tone circuit(not shown) is closed to transmit a busy tone to the calling station.Contact S2 prevents the operation of relay X after relay K releases. Y

A forced release of the register-translator may occur at any stage ofits use in case an interval of from 18 to 27 seconds has elapsed afterthe operation of relay BB. At contact 17118, the upper winding of relayZA is connected to an impulse conductor to which ground impulses of .'75second duration are connected at intervals of 9 seconds. The rst groundimpulse after relay BB operates causes the operation relay ZA sucientlyto actuate only its contact sal, at the end of the impulse relay ZA iscompletely operated by its windings in series. The next impulse, 9seconds later, energizes the upper winding of relay ZB suiiciently toactuate only its contact zbl and at the end of the impulse relay ZB iscompletely operated by its windings in series. At the front contact ofspring zb2, the upper winding of relay R is then connected to the 9second impulse conductor; and, after 9 seconds more, the next impulsecauses the operation of relay R. The release of the register-translatoris thereby forced by the operation of relay R irrespective of the stageof the call. In such a case, if the selector OS4 has seized an idleoutgoing junction, the calling subscriber could obtain completion of thecall by dialing whatever digits remained to be dialed.

If the calling subscriber releases the connection at any time after theline is connected to relay RA of the register-translator, relays RA, RBand BB release. Relay R is then operated through contact onZ and bbl tocause the release of the link and the return of all switches to normalas hereinbefore described.

What is claimed is:

l. In a telephone system, a selector switch for use in establishingdesired connections, groups of lines connected to the bank of saidswitch, means for advancing the brushes of said switch to select anydesired one of said groups of lines, means for hunting for an idle linein a selected group, a register switch, and means effective if no idleline is found in a selected groupv for operatively associating saidregister switch with said selector switch..

2. In a telephone system, a selector switch for use in establishingdesired connections, groups of lines connected to the bank of saidswitch, means for advancing the brushes of said switch to select anydesired one of said groups, means for hunting for an idle line in aselected group, a register-translator comprising a register switch and atranslator switch, and means eective if no idle line is found in aselected group for operatively associating said register-translator withsaid selector switch.

3. In a telephone system, according to claim l, means for advancing saidregister switch and selector switch simultaneously one step at a time.

4. In a telephone system, according to claim l,

Vmeans comprising vertical commutatore of said selector and registerswitches ior identifying the group in which no idle line was found.

5. In a telephone system, a two-motion selector switch for use inestablishing desired connections, groups of lines connected to the bankof said switch, means for advancing the brushes of said switch to selectany desired one of said groups of lines, means for hunting for an idleline in a selected group, a register switch, means eiective if no idleline is found in a selected group for operatively associating saidregister switch with said selector switch, means comprising verticalcommutatore of said selector and register switches for identifying theterminal level in which said selected group is located, and means foradvancing said register switch and selector switch simultaneously onestep at a time to complete the identificationof said group.

6. In a telephone system according to claim 1, means for advancing saidregister switch to identify the group in which no idle line was found,and means comprising a translator switch for determining the identity ofanother one of said groups which other group constitutes an alternativeroute to the group in which no idle line was found.

7. In a telephone system according to claim 1, means for advancing saidregister switch to identify the group in which no idle line was found,and means effective upon completion of the identication of said groupfor returning said selector to normal.

8. In a telephone system according to claim 1, means for advancing saidregister switch to identify the group in which no idle line was found,means effective upon completion of the identification of said group forreturning said selector to normal, and means comprising a translator pswitch for controlling the reoperation of said selector to selectanother one of sai-d groups which other group constitutes .analternative route to the group in which no idle line was found.

9. In a telephone system, a selector switch having groups of linesconnected to its terminal bank, each group leading to a differentexchange, means for advancing the brushes of said switch to select theone of said groups which leads to a called one of said exchangesv andfor advancing the. brushes to hunt for an idle line in the selectedgroup, a register switch, means effective if no idle line is found inthe selected group for operatively associating said register switch andselector switch, means for advancing said register switch to identifythe group in which no idle line was found, and translator means fordetermining the code for controlling the completion of the desiredconnection over an alternative one of said groups and through anotherone of said exchanges to said called exchange.

10. In a telephone system, a selector switch having groups of linesconnected to its terminal bank, each group leading to a differentexchange, means for advancing the brushes of said switch to select anydesired one of said groups and for advancing the brushes to hunt for anidle line in a selected group, a register-translator comprising aregister switch and a translator switch, means effective if no idle lineis found in a selected group for operatively associating said selectorswitch with said register-translator, means for advancing said registerswitch to identify the group in which no idle line was found, and meanscomprising said translator switch for determining the code of analternative route over which the desired connection can be established.

11. In a telephone system, a selector switch having groups of linesconnected to its terminal bank, each group leading to a differentexchange, means for advancing the brushes of said switch to select anydesired one of said groups and for advancing the brushes to hunt for anidle line in a selected group, a register switch, means effective if noidle line is found in a selected group for operatively associating saidregister switch and selector switch, means for advancing said registerswitch to identify the group in which no idle line was found, meanseffective upon completion of the identification for returning saidselector switch to normal position, and translating means forcontrolling the reoperation of said selector switch to select analternative group of trunks over which the desired connection can becompleted.

12. In a telephone system, a selector switch having groups of linesconnected to its terminal bank, each group leading to a differentexchange, means for advancing the brushes of said switch to select anydesired one of said groups and for advancing the brushes to hunt for anidle line in a selected group, a register switch, means effective if noidle line is found in a selected group for operatively associating saidregister switch and selector switch, means for advancing said registerswitch to identify the group in which no idle line was found, meanseffective upon completion of' the'identincation for returning saidselector switch to normal position, and translating means fordetermining the codev of an alternative route.

18. In a telephone system, a selector switch having groups oflines'connected to its terminal bank, each group leading to a differentexchange, means for advancing the brushes of said switch to select anydesired one of said groups and for advancing the brushes to hunt for anidle line in a selected group, a register switch, means effective if noidle line is found in a selected group for operatively associating saidregister switch and selector switch, means for advancing said registerswitch to identify the group in which no idle line was found, meanseffective upon completion of the identification for returning saidselector switch to normal position, and translating means fordetermining the code of an alternative route, for transmitting the firstdigit of said code to control the reoperation of said selector switchand selection of a group leading to a tandem office, and fortransmitting the remaining digits of said code to control the extensionof the con,- nection through the tandem oflice to the wanted office.

14. In a telephone system, groups of selector switches for use incompleting desired connections, groups of lines multipled to theterminal banks of a group of said selectors, each of said groups leadingto a different exchange, means in each of the selectors for advancingits brushes to select any desired one of said groups of lines and foradvancing its brushes to hunt for an idle line in a selected group,translators, links for connecting the translators to the selectors,means effective upon one of said selectors finding no idle line in aselected group for starting the operation of a link to operativelyassociate one of said translators with` said selector, register means insaid associated translator for determining the group in which no idleline was found, means effective upon completion of the identification ofsaid group for causing they return of said selector to normal, and meansin said translator for sending the code digits of an alternative routefor controlling the reoperation of said selector to select a group oflines to a tandem exchange and for controlling the extension of theconnection through said tandem exchange to the called exchange.

15. In a telephone system, a two-digit selector switch having groups oflines connected toits terminal bank, each group leading to a differentexchange, means for receiving digit impulses for controlling theoperation of the switch, means responsive to a first one of two digitsfor advancing the brushes of the switch to a corresponding level of theterminal bank, means responsive to .the second one of said digits foradvancing the brushes to select a desired group in a selected level,means for advancing the brushes to hunt for an idle set of terminals insaid desired group, translators, means effective if the brushes of saidselector switch are advanced to the last set of terminals in the desiredgroup without nding an idle line for operatively associating an idle oneof said translators with said selector, a register switch in saidtranslator, means for advancing the brushes of said register switch to alevel corresponding to said selected level of said selector switch,means for advancing the brushes of said register switch one step at atime and for simultaneously advancing the brushes of said selectorswitch one step at a time until the brushes of said selector switchreach the eleventh rotary position, the terminal with which the brushesof said register switch are then in engagement being indicative of thedigit code by which said desired group of lines is selected.

16. In a telephone system, a group of two-digit, selector switches foruse in establishing desired connections, another group of such switches,groups of lines connected to the banks of the switches in one group ofselectors, other groups of lines connected to the banks of the switchesin the other group of selectors, each group of lines leading to adiierent exchange, means in each selector for advancing its brushes toselect a desired level, a desired group of terminals in said level andan idle line in said group, translators, means eiective upon` thebrushes of one of said selectors being advanced to the last set ofterminals in` a desired group without nding an idle line for operativelyassociating said selector with an idle one of said translators, aregister switch in said translator, means for advancing the brushes ofsaid register switch to a level corresponding to the level selected bythe brushes of said selector switch, means for simultaneously advancingthe brushes of said register switch and the brushes of said selectorswitch step-bystep until the brushes of said selector reach the eleventhrotary position in the level, and means eiiective only if said selectoris in one of said groups for advancing the brushes of said register onestep without at the same time advancing the brushes of said selectorswitch before said simultaneous stepping of said switches begins.

17. In a telephone system, groups of selector switches used incompleting desired connections, different groups of lines multipled tothe banks of each group of selectors, each group of lines leading to adii'erent exchange, means in each selector for advancing its brushes toselect a desired level and an idle line in the desired group, atranslator, link means effective upon all of the lines in a desiredgroup being found busy by one of said selectors for operativelyassociating said translator and selector, group identifying terminalsfor said selectors, a register switch in said translator, groups ofterminals in the bank of said register switch, the terminals in eachgroup being multipled to the group identifying terminals of theselectors in a different one of said groups of selectors, and meansincluding said group identifying terminals for advancing the brushes ofthe register switch to the terminal corresponding to groups in which theselector found all lines busy.

ESMOND P. G. WRIGHT.

GEORGE C. HARTLEY.

PAUL IAN WYNDHAM.

